Both plastic and metal closures for various bottles and containers which include a tamper-evident feature have been known for many years. In most cases, this tamper-evident feature comprises a lower shoulder or skirt portion of the closure which is in some way intended to fracture or break upon removal of the closure from the container, so that it then becomes evident that the container has been opened. While a large number of these closures have been known in the past, on a commercial basis, and particularly in connection with soda bottles and other such containers maintained under significant pressures, up until quite recently metal closures have predominated. These include closures such as shown in U.S. Pat. No. 3,812,991 which issued on May 28, 1974 to the Coca Cola Company, and many others.
The many problems encountered in connection with the use of metal closures, however, have been significant. They primarily relate to the fact that in an unacceptably large proportion of cases, removal of the closure does not result in a clean and efficient fracture of the lower skirt portion, therefore making removal of the closure quite difficult and/or completely eliminating the tamper-evident feature. In addition, the cost of metal closures has recently increased dramatically, and the search for efficient plastic closures has therefore intensified.
In connection with plastic closures of this type, again a large number have been known in the past, but no commercial closure has been found which can be applied in a single step to the container or bottle, (i.e. such closures generally require a two-step application procedure), and can at the same time result in efficient breaking or fracturing upon its removal. One recent commercial closure which is now widely utilized is that of U.S. Pat. No. 4,033,472 to Albert Obrist AG, which issued on July 5, 1977. Such closure, however, again suffers from both of these infirmities. In the first place, it requires a two-step application procedure, i.e., initial application of the closure to the bottle followed by a heating process whereby the lower depending bead 4 is deformed against the surface of the bead or collar on the bottle itself, as shown in FIG. 4 thereof. In addition, it has again been found that such closures, although used commercially, do not fracture properly in an unacceptable proportion of cases. Several other issued patents which include such two-step application procedures include U.S. Pat. No. 3,673,761 assigned to Ciba-Geigy AG, and U.S. Pat. No. 3,788,509 to Keeler, which includes a separate heating step for producing the weakened zones themselves.
Among those patents which do show a one-piece plastic closure, which does not require such a heal sealing step, are those to Hamberger, namely U.S. Pat. Nos. 2,162,711 and 2,162,712. These patents, however, are directed to closures which include a weakened portion defined by corresponding grooves on the shoulder portion (see FIG. 1 thereof) of the depending skirt 23. In such closures, fracturing thus occurs in a vertical direction with respect to the closure, and tangentially with respect to the lugs 18 to which the skirt is attached. In addition, the skirt portion in this patent appears to be constructed so as to be thinner than the upper walls thereof. Additional such closures are also shown in the Schauer patents, namely U.S. Pat. Nos. 2,162,752 and 2,162,754. None of these patents thus teach the structure of a commercially acceptable product.
There are yet another group of patents directed to such closures which rely upon interlocking teeth or serrations in order to effect the fracture of the closure. For example, French Pat. No. 1,347,895 includes a ratchet or lug means on the breakaway skirt portion 2 thereof as well as on the bottle bead, and German Pat. No. 2,349,265 also includes lugs 16 which extend inwardly from depending skirt 13 to aid in fracturing at the point of weakness thereon. Reference in this regard is also made to U.S. Pat. Nos. 3,980,195, 3,924,769 and 4,126,240.
In U.S. Pat. No. 4,343,408 to Psaszar there is disclosed a tamper-evident plastic closure which allegedly obviates certain problems of the prior art, and may be applied to the neck of the container in a one-step twisting operation. All of the heretofore tamper-evident closures having internal threads for threadable engagement with a neck having extended threads of a container have required the threading of the closure onto the neck thereof with certain concomitant problems. If an excess of rotational force is used, the closure may fracture thereby permitting subsequent leakage of the contents thereof, or may present problems in removing the closure from the container. Obviously, if less than an appropriate rotational force is used, leakage, or reduced shelf life, etc., may result. Additionally, assemblies for positioning and twisting closures onto necks of containers are complicated and require constant maintenance to insure proper processing of the closure onto the neck of the container.